Power press machines, commonly called punch presses, typically use a flywheel, driven by a relatively small motor, as the kinetic energy source for driving a ram. The lower end of the ram is connected to an upper die. When the ram is cycled or tripped, the flywheel drives the ram downwardly forcing the upper die towards a workpiece placed between the upper die and a lower die.
Press machines are typically provided with an interlocked barrier guard assembly for the safety of the operator. These barrier guard assemblies may include one or two doors or other barriers which must be in place, preventing access to the die area, before the machine is allowed to cycle the ram.
Unfortunately, even press machines with interlocked barrier guard assemblies can be unsafe. Press machines can malfunction so that the ram unexpectedly and unintentionally performs a successive stroke, in what is known as a multiple trip. This type of malfunction can have catastrophic consequences for the operator. Severe industrial accidents, often involving amputation, are an unfortunate but a relatively common result of such a malfunction.
Many accidents also result from the operator intentionally removing or overriding the safety interlocking mechanism on the machine. In addition, when mounting the upper die to the lower end of the ram the machine must often be activated for a partial cycle to jog the ram into position. Unfortunately, sometimes the machine is inadvertently cycled while the operator's hands are in the die area resulting in injury to the operator.
Thus, although the prior art has recognized the dangerous aspects of press machines, until now there has existed no sure way of protecting the operator from injury resulting from multiple trips, malfunctions or operator error.